The present invention relates to a substrate processing apparatus for performing substrate processing such as developing processing and the like, for example, for a substrate and a method thereof.
A mask for forming a predetermined pattern on a front face of a semiconductor wafer (hereinafter, referred to as "wafer") or a glass substrate (LCD substrate) of a liquid crystal display is obtained by applying a resist to a front face of a substrate such as a wafer or the like and then irradiating rays of light, electron rays, ion beams, or the like to the resist surface, and performing developing. The developing processing here is performed by dissolving portions irradiated with light or the like or portions without such irradiation in an exposure process with use of an alkaline water solution or the like, and conventionally it has been performed by a method shown in FIG. 18.
In the conventional method, a substrate, for example, a wafer W is suction-held, for example, on a spin chuck 11 having a vacuum suction function, and a supply nozzle 13 in which many discharge holes 12 are arranged along a length corresponding to a diameter of the wafer W is positioned so that the discharge holes 12 are placed above the wafer surface by 1 mm at the central portion of the wafer W. Then, a developing solution 10 is supplied to the center of the wafer surface from the discharge holes 12 to thereby perform solution heaping as shown in FIG. 18. Subsequently, the wafer W is made to half-rotation (180-degree rotation) while the developing solution 10 is supplied from the discharge holes 12.
Thus, the developing solution which has been first heaped at the central portion of the wafer is spread out and simultaneously the developing solution 10 is newly supplied, resulting in formation of a solution film of the developing solution 10 with a predetermined thickness over the entire wafer surface. After the heaping of the developing solution 10 is performed, the wafer W is left standing, for example, for 60 seconds, and then a rinse solution is supplied onto the wafer surface to rinse away the developing solution, whereby the developing is performed.
Explaining briefly a conventional developing apparatus in which the above-described developing processing is performed with reference to FIG. 19, the spin chuck 11 is surrounded by a cup 14 for preventing the developing solution 10 from splashing out. A filter unit 15 formed by combination of a filter and a fan is provided above the cup 14 and a current plate 16 in which many air holes 16a are formed is provided between the filter unit 15 and the cup 14.
An exhaust passage 17 is connected to the cup 14, and part of air which has been exhausted by the exhaust passage 17 is circulated to be supplied to the filter unit 15 via a filter apparatus not shown for eliminating impurities and performing adjustment to a predetermined temperature and humidity to be supplied from the filter unit 15 toward the cup 14 while forming downflow. The air from the filter unit 15 from which impurities have been eliminated and which has been adjusted to the predetermined temperature and humidity passes through the current plate 16, thereby being supplied to the cup 14 side with being increased in uniformity. The downflow of air, which is adjusted with high accuracy, is formed to make developing solution temperatures and evaporation speeds uniform.
However, for example, in the case of using an ion beam resist, developing unevenness occurs in the above-described developing method, whereby developed line width varies depending on the position, which causes a disadvantage of, for example, an irregularity in line width of about 4 nm between an area close to the center of the wafer and a rim portion thereof. From a study of a cause of the above, it is conceivable that temperature distribution occurs in the developing solution 10 within the plane of the wafer because degrees of proceeding of the developing depends on the temperature of the developing solution 10.
In other words, the developing solution 10 is adjusted to a temperature of, for example, about 23.degree. C., but water contained in the developing solution 10 evaporates while the wafer W is subjected to the solution heaping and then left standing, whereby latent heat in the developing solution 10 is lost, and thus the temperature of the developing solution 10 falls with time. Meanwhile, it is conceivable that the temperature of the rim area falls to be lower than that of the area close to the center of the wafer W within the plane due to the formation of the downflow of the aforesaid air which has been adjusted with high accuracy. More specifically, by the formation of the downflow, air currents flow from above seeing from the wafer W. The air currents which have blown against the wafer W flow toward the outer periphery side thereof along the wafer face as shown in FIG. 20, whereby an airflow amount to the rim area becomes larger than that to the area close to the center. Therefore, it is presumed that heat of evaporation in the rim area is larger than that in the area close to the center within the plane of the wafer W, so that an amount of heat radiation in the rim area becomes larger than that in the area close to the center, resulting in a high degree of fall in temperature of the rim area.
Therefore, it is presumed that temperature difference in the developing solution 10 of about 1.degree. C. occurs between the area close to the center of the wafer and the rim portion at the start of a rinse, whereby there occurs unevenness in the developing state, resulting in occurrence of a bad influence of variations in finished measurements.